European Patent Publication EP 0,240,075 B discloses a method and apparatus for minimizing weft waste, whereby at least two weft thread supply mechanisms are used for producing the fabric.
According to the known method substantially the following steps are performed.                1. At least two weft threads, including one first and one second weft thread, are to be sequentially inserted into the loom shed. Each weft thread is clamped by a respective clamp of a corresponding weft presentation lever of a presentation and clamping mechanism, whereby the presentation levers are in a position A.        2. A weft thread selector chooses in response to a control program between the two weft threads for presenting one of the two weft threads to a weft insertion gripper.        3. The respective presentation lever is moved into a second or presentation position B thereby bringing the selected weft thread into the moving path of the weft insertion gripper which takes over the weft thread for insertion into the loom shed.        4. The presentation lever is then moved into a position C which is located close to the insertion edge of the fabric on a line that is an extension of the beat-up line or an extension of the interlacing points along the beat-up line of a fabric being woven.        5. At this point the weft thread taken over by the gripper is still connected to the weft supply. After the insertion into the loom shed and after the beat-up the weft thread is clamped and held in the clamped position C by the respective clamp.        6. The beat-up weft thread is then cut between the selvage edge of the fabric and the clamp that is still in position C, thereby severing the trailing end of the inserted weft thread from the leading end of the clamped weft thread held ready for the next insertion.        7. The respective presentation lever, following the cutting of the weft thread, is held in the position C or it is moved back into the position A.        
The above conventional method and the conventional apparatus for performing the known method have a significant disadvantage, namely that each type of weft thread to be inserted into the loom shed necessarily has a different length of weft waste. This is so because each weft presenting clamp of a plurality of weft presenting clamps has a different spacing from the fabric weft entrance edge. More specifically, the weft clamp positioned closest to the fabric edge yields the smallest length of weft waste. The weft waste for the next weft thread is larger than that of the first weft thread and so on so that the weft waste increases from weft thread to weft thread in a group of a plurality of weft threads. The increasing weft waste lengths are determined by the construction of the loom and present a substantial disadvantage. A further conventional disadvantage is seen in that the weft thread is cut in the area where the reed performs its beat-up. As a result, the weft thread must be pulled out all the way to the interlacing point. In order to reduce the weft waste, the known apparatus employs a pull-back mechanism that pulls back the next weft thread to be inserted after it has been cut near the interlacing point or beat-up line. The weft pull back mechanism is additionally necessary to maintain the required weft tension for the next following weft insertion.
The above described functions are performed by a conventional apparatus that has a mechanism for presenting and clamping the weft threads in a gripper loom. The known apparatus comprises essentially a weft presenting lever equipped with a thread clamp for each weft thread to be inserted into the loom shed. The weft presenting levers are positioned next to each other and approximately in parallel to the fabric edge or selvage on the weft insertion side of the loom shed. The clamp of the first weft presenting lever is positioned closest to the fabric edge when the clamp is in the positions A and C. The clamp on the last weft presenting lever is positioned furthest away from the fabric edge. Thus, it is clear that the free length of weft thread becomes longer and longer starting at the first position of the first clamp and increasing with the following clamps. The weft thread cutter is mounted in a fixed position next to the fabric edge and cuts longer and longer weft thread ends. Moreover, as a rule, the longer the weft thread between the clamp and the weft cutter, the smaller is the thread tension. However, it is desirable that a certain assured tension is present in the weft thread as it is cut. As a result, the known apparatus does not ensure that the selvage along the weft entrance side of the loom shed is always meeting the required quality standards.
German Patent Publication DE-OS 25 31 954 discloses a controllable weft thread clamping mechanism comprising a plurality of clamping points. Each clamping point is displaceable or adjustable relative to a reference plane. Further, the clamping points are arranged at equal spacings from one another and one above the other. One clamping position at a time can be shifted into the reference plane. Each clamping position is constructed to cooperate with a controlled weft thread selector. These weft thread selectors are known as such. This combination of a clamping position with a controlled weft thread selector has the advantage that the weft thread to be inserted into the loom shed can be transported into a first reference plane where the weft insertion gripper can seize the weft thread without any problems. Another advantage of the known apparatus is seen in that the respective clamping position can be moved into a second reference plane which corresponds to the position of the interlacing point at the fabric edge. This conventional feature makes it possible that when the weft thread is beat-up to the beat-up line of the fabric, the weft thread is clamped by the respective clamping position of the clamping mechanism and is held in tension at the entrance side of the loom shed between the fabric edge and the clamping position. This tension in the weft thread at this position is advantageous for the cutting by the weft cutter or scissors mounted between the clamping position and the fabric edge. However, the weft waste cannot be minimized with such an arrangement because the weft threads cannot be presented directly to the weft insertion gripper.
German Patent Publication DE 30 42 053 C1 discloses a weaving loom with an apparatus for reducing weft thread waste. However, the known weaving loom employs rather complicated features or mechanisms for the reduction of weft waste. These mechanisms in combination with the cutter for severing the beat-up weft thread is technically quite involved and correspondingly prone to trouble. In the known apparatus the cut-off trailing end of the inserted and beat-up weft thread is stretched by pneumatically effective nozzles, which due to their pneumatic nature require a weft thread end that cannot be relatively short.
German Patent Publication DE 197 39 853 C2 discloses a weft thread presenting and clamping mechanism with a plurality of weft presenters each of which is equipped with a clamp. These presenters and clamps are arranged in the loom for cooperation with at least one weft pull-back mechanism. The cooperation with the pull-back mechanism is such, that all weft threads of a group of weft threads are presented approximately in the same point to the weft insertion gripper in order to realize a minimum of weft waste. All wefts of a group are to be inserted into a loom shed in a predetermined sequence as controlled weft selector.